emacs: Add 'current' generation parameter.

* emacs/guix-main.scm (generation-param-alist): Add 'current' parameter.
* emacs/guix-base.el (guix-param-titles): Add title for 'current' parameter.
* emacs/guix-info.el: Display 'current' parameter.
  (guix-generation-info-current, guix-generation-info-not-current): New faces.
  (guix-generation-info-insert-current): New procedure.
* emacs/guix-list.el: Display 'current' column.
  (guix-generation-list-get-current): New procedure.

emacs/guix-base.el

@@ -107,6 +107,7 @@ Interactively, prompt for PATH.  With prefix, use
      (id                . "ID")
      (number            . "Number")
      (prev-number       . "Previous number")
+     (current           . "Current")
      (path              . "Path")
      (time              . "Time")))
   "List for defining titles of entry parameters.

emacs/guix-info.el

@@ -136,6 +136,7 @@ number of characters, it will be split into several lines.")
      (location          guix-package-info-insert-location))
     (generation
      (number            guix-generation-info-insert-number)
+     (current           guix-generation-info-insert-current)
      (path              guix-info-insert-file-path)
      (time              guix-info-insert-time)))
   "Methods for inserting parameter values.
@@ -161,7 +162,7 @@ argument.")
     (output name version output synopsis path dependencies location home-url
             license inputs native-inputs propagated-inputs description)
     (installed path dependencies)
-    (generation number prev-number time path))
+    (generation number prev-number current time path))
   "List of displayed entry parameters.
 Each element of the list should have a form:
 
@@ -613,6 +614,16 @@ ENTRY is an alist with package info."
   "Face used for a number of a generation."
   :group 'guix-generation-info)
 
+(defface guix-generation-info-current
+  '((t :inherit guix-package-info-installed-outputs))
+  "Face used if a generation is the current one."
+  :group 'guix-generation-info)
+
+(defface guix-generation-info-not-current
+  '((t nil))
+  "Face used if a generation is not the current one."
+  :group 'guix-generation-info)
+
 (defun guix-generation-info-insert-number (number &optional _)
   "Insert generation NUMBER and action buttons."
   (guix-info-insert-val-default number 'guix-generation-info-number)
@@ -632,6 +643,12 @@ ENTRY is an alist with package info."
    "Delete this generation"
    'number number))
 
+(defun guix-generation-info-insert-current (val entry)
+  "Insert boolean value VAL showing whether this generation is current."
+  (if val
+      (guix-info-insert-val-default "Yes" 'guix-generation-info-current)
+    (guix-info-insert-val-default "No" 'guix-generation-info-not-current)))
+
 (provide 'guix-info)
 
 ;;; guix-info.el ends here

emacs/guix-list.el

@@ -65,6 +65,7 @@ entries, he will be prompted for confirmation."
      (number 5
              ,(lambda (a b) (guix-list-sort-numerically 0 a b))
              :right-align t)
+     (current 10 t)
      (time 20 t)
      (path 30 t)))
   "Columns displayed in list buffers.
@@ -93,8 +94,9 @@ this list have a priority.")
      (synopsis    . guix-list-get-one-line)
      (description . guix-list-get-one-line))
     (generation
-     (time . guix-list-get-time)
-     (path . guix-list-get-file-path)))
+     (current     . guix-generation-list-get-current)
+     (time        . guix-list-get-time)
+     (path        . guix-list-get-file-path)))
   "Methods for inserting parameter values in columns.
 Each element of the list has a form:
 
@@ -735,6 +737,11 @@ Also see `guix-package-info-type'."
   (define-key map (kbd "i")   'guix-list-describe)
   (define-key map (kbd "d")   'guix-generation-list-mark-delete))
 
+(defun guix-generation-list-get-current (val &optional _)
+  "Return string from VAL showing whether this generation is current.
+VAL is a boolean value."
+  (if val "(current)" ""))
+
 (defun guix-generation-list-show-packages ()
   "List installed packages for the generation at point."
   (interactive)

emacs/guix-main.scm

@@ -638,13 +638,14 @@ See 'entry-sexps' for details."
 
 (define (generation-param-alist profile)
   "Return an alist of generation parameters and procedures for PROFILE."
-  (list
-   (cons 'id          identity)
-   (cons 'number      identity)
-   (cons 'prev-number (cut previous-generation-number profile <>))
-   (cons 'path        (cut generation-file-name profile <>))
-   (cons 'time        (lambda (gen)
-                        (time-second (generation-time profile gen))))))
+  (let ((current (generation-number profile)))
+    `((id          . ,identity)
+      (number      . ,identity)
+      (prev-number . ,(cut previous-generation-number profile <>))
+      (current     . ,(cut = current <>))
+      (path        . ,(cut generation-file-name profile <>))
+      (time        . ,(lambda (gen)
+                        (time-second (generation-time profile gen)))))))
 
 (define (matching-generations profile predicate)
   "Return a list of PROFILE generations matching PREDICATE."